Looks like a Platy, but a 2-liter flask weighs only 0.8 ounce and costs $4.

Overview

It's basically the same technology as a Platypus flask, at two-thirds the weight and a fraction of the cost. A 2-liter MPACK flask (without cap) weighs 0.8 ounce and costs $4.

The MPACK AquaFlo Hydration System uses a “disposable” flask that weighs just 0.8 ounce (2-liter size) and costs just $4 each.

Disposable hydration system? That's the marketing approach. The rationale is that many existing hydration systems are hard to clean, accumulate contaminants with age, and are pricey to replace. So the MPACK solution is to buy them cheap and recycle them when they get worn or contaminated. Of course, one could alternatively give it reasonable care and make it last a fairly long time.

The flask is made of a co-extruded formulation of low-density polyethylene (inside) and nylon (outside) that is claimed to be durable and odor/taste free. It has a screw fitting that looks the same as a Platypus flask, but it's not (we tested it). The MPACK drink tube and cap will not fit on a Platy flask, or vice-versa. Bummer.

The manufacturer claims the flasks are very durable and they have not had one fail yet, but they are also targeted to be “disposable”, so time will tell on how long they actually last. A competing 2 liter Platypus flask weighs about 1.3 ounces and costs about $10. However, it has a lifetime guarantee, backed by Cascade Designs, which is an important point.

We suggested that they create an MPACK with two vertical compartments and two caps so hikers can put water in one half and a performance drink in the other. They liked the idea.